Please can someone help me with my UC payment

[Cupofteaonesugar]

Employer is paying us £1000 COLP
I normally earn £870 after deductions
I normally get around £670 top up from UC for having 2 children, single parent.

How do I work out what UC payment I would get after tax etc due to this one off payment?

We have been given The option to receive the payment in the form of vouchers via our rewards account at work. I'm going to opt for this as I figure then it will not effect my UC as it won't be reported and I can use keep what I would have spent to help support me in other ways.
I'm thinking I would see mucb if it once tax NI student loan and then putting away my normal UC payment has evened out otherwise!

UC use what your paid to work out your UC award so any "wages" that go through HMRC will be used in that calculation. It will be calculated at the taper rate I believe same as your normal wages.

For each additional pound you are paid, your normal Uc payment will reduce by 55p.