"only one day left for css 2021 registration so can i apply for it"

Yes. You can apply for it. Till tomorrow's midnight. But apply ASAP because FPSC website is prone to crashing under heavy traffic/load.

because there is also need to send hard copy of documents to fpsc head office within 10 days of closing date

Complete online application tonight or tomorrow. Print it and send it via courier. No problem.

For future queries, post your question in relevant thread and section

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