Reimbursed expenses cutting into trading allowance?

Hi, I am self employed, working on events. Sometimes I purchase things on behalf of my employer, and receive reimbursement. For example, paying for posters for an event to be printed. I include these expenses on my invoices, along with the receipts, and then get paid a single sum for both my billed hours, and the costs I have incurred on behalf of my employer. When filling in my tax return, I can see that it says you can only use either the £1,000 trading allowance or use allowable expenses. If I use the trading allowance does that mean I have to pay tax on the reimbursements I have received from my employer for purchases made on their behalf? If so, that seems like I am being penalised for purchasing things on behalf of my employer. Is this correct? Thank you!

Hi
If claiming the trading allowance then you cannot claim any additonal expenses.
By claiming this, this would then cover the reimbursent of the purchases.
Either way, you need to show the total income to include the purchases made as you have been paid for these.
You are not being penalised.