The Iron made one change going into the game, with Mason O'Malley coming in for the injured Lewis Thompson.
The hosts won an early free-kick on the right side as Omar Bugiel was fouled. It saw an inviting in-swinging free-kick into the box from Ron Milsom, with Manny Onariase rising highest to tower his header clear of danger.
In the third minute, Harry Bunn kept possession down the left flank after Joe Nuttall's pass and eventually sent a cross in for Nuttall, who got a touch to the ball but saw Dean Bouzanis equal to his effort.
With four minutes gone, Donovan Wilson got into the area on the right side for Sutton, but snatched at his shot, with the ball going wide of Rory Watson’s left post.
With eight minutes played, Nuttall received the first yellow card of the game as he challenged for a header with Louis John. The centre-half went down and the referee obliged.
The hosts then got into the area down the left, with a powerful low cross pushed away by Watson and cleared by Ryan Delaney.
Liam Feeney won possession with 12 minutes gone and tried to play Bunn through, but a block thwarted that. Possession was then won back and Tyrese Sinclair pressed down the left, with his shot deflected wide for a corner.
Onariase won first contact from the set-play, with Jai Rowe lurking for the second ball. It arrived back at Onariase who headed back into the area, but the hosts got the ball clear.
After 15 minutes, the ball almost dropped twice for Sinclair in the area after Delaney held up play from an Iron free-kick. The second time he went for the acrobatic overhead kick, but connected with Bugiel as he cleared the ball, with a free-kick awarded to the hosts.
With 24 minutes gone, the home side pushed forward and had a chance which Milsom placed wide of Watson's left-hand post from the edge of the area.
Soon after, O’Malley nipped in as a low cross came into the box. Play continued, with Watson then conceding a corner. From the corner, O’Malley headed off the line before Onariase hooked clear.
Oh half an hour, the hosts won a penalty as Onariase was penalised for a foul on Bugiel, which was converted by Milsom. lthough Watson got a hand to it he couldn't keep it out.
A minute later, there was a second for the hosts as Will Randall bent a 25-yard effort across goal and into the far corner.
With 36 minutes played, Nuttall cushioned the ball to Bunn, who skipped past one challenge before slipping in Sinclair on the left of the area. He won a corner.
From it, a Sutton boot almost connected with Onariase’s face as he went to win the header from the corner. Bouzanis made the save as the header went towards goal, resulting in another corner for the Iron.
Feeney’s delivery into the six yard box was met by the run of Jai Rowe, who sent his header narrowly over the bar.
With 38 minutes gone, Joe Kizzi fired a third into the roof of the net as he was slipped into the area on the right side.
On 43 minutes, Sinclair was left on the deck following an off the ball incident with Sutton skipper Craig Eastmond, which none of the officials claimed to have seen.
At half-time, Nuttall and Bunn were replaced by Rekeil Pyke and Harvey Cribb, making his Iron first team debut at the age of 16.
In the first minute of the second period, Onariase’s last ditch challenge prevented an initial shot on goal before Delaney got his body in the way of a later effort.
Sinclair slid in inside the box to concede a corner soon after. He remained on the floor in the aftermath, but was soon gingerly back to his feet, not requiring treatment.
Cribb then headed the ball away from danger as the corner was delivered into the penalty area.
With 56 minutes gone, David Ajiboye played his way into the area and cut back onto his left foot. Bugiel then took the ball from him, sending his first time effort over the bar from 12-yards.
With 61 minutes gone, Sutton's Randall added his second goal of the game, as the ball was squared to him 10-yards from goal.
In the 67th minute, Sinclair charged down a clearance and then had a go from 20-yards. His shot took a deflection before being saved by Bouzanis.
Hackney replaced Grant on 70 minutes for Scunthorpe's final change of the afternoon.
Three minutes later, Sinclair brought the ball down on the edge of the box before sending a half-volley wide of the target.
Then, soon after, Cribb cut in from the left and sent a low shot goalwards which Bouzanis got down to save.
The Iron pulled a goal back in the 79th minute when Pyke’s ball across the box from the right was turned into his own net by Harry Beautyman.
United return to action next Saturday with a trip to take on Crawley Town.
SUTTON: Bouzans, Kizzi, John (Rowe, 64), Goodliffe, Milsom, Randall, Davis, Eastmond (Beautyman, 67), Ajiboye (Korboa, 74), Wilson, Bugiel.
SUTTON SUBS NOT USED: Nelson, Dundas, Boldewijn, Wyatt.
IRON: Watson, Millen, O'Malley, Delaney, Onariase, Nuttall (Pyke, 45), Rowe, Bunn (Cribb, 45), Sinclair, Feeney, Grant (Hackney, 70).
IRON SUBS NOT USED: Collins, Burns, Moore-Billam, Young.
ATTENDANCE: 2,870 (313 away).
