一点回答
基本上来说，几个准证之间的差别是以学历和工资水平来做主要区别的
P Pass一般是签发给有一定的学历的专业人士或者管理人员，按照工资的高低具体还分P1、P2两种，工资高于S$7000的P1，工资水平处于S$3500到S$7000的P2
Q1 pass签发对象也是有一定的学历的专业人士，工资高于S$2500的
S Pass的工资必须在1800以上，好像有不少限制
WP一般是签发给普通的工人，比如工地工人等，这个应该是限制最多的
平常大家说的SP一般是指student pass(学生准证),S Pass一般不叫SP
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
WP应该是不能申请PR的，其他的几个似乎都可以(P, Q or S work pass holders;)，至于“不能离境或怀孕之类”这个我没有具体看，不大清楚。
下面你提到的缴税，不管是PR还是持其他什么准证，都是要上税的，具体的上税标准取决于在新加坡上班的天数，少于60天的可以免税，60-183天的税率是15%,超过183天的税率根据年薪算，2万之内的那部分好像是免税的，之后一段一段交(比如说工资超过2万的，前2万是免税的，2万到3万那部分税率3.75%)，是WP和S pass的好像每个月还要交什么劳工税之类，而且每个公司能够雇佣的人数有一定限制，不过具体我也不大清楚。
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以下是从人力部(MOM)官方网站拷贝下来的关于不同工作准证的信息
EMPLOYMENT OF LONG-TERM SOCIAL VISIT PASS HOLDER
The Long-Term Social Visit Pass holder is required to obtain an Employment Pass or a Work Permit in order to work in Singapore.
P Pass - For foreigners who hold acceptable degrees, professional qualifications or specialist skills and are seeking professional, administrative, executive or managerial jobs.
*
A P1 Pass will be issued if the applicant's monthly basic salary is more than S$7,000.
*
A P2 Pass will be issued if the applicant's monthly basic salary is more than S$3,500 and up to S$7,000.
Q1 Pass - For foreigners whose monthly basic salary are more than S$2,500 and possess acceptable degrees, professional qualifications or specialist skills.
S Pass (A new category of Work Pass which replaces the Q2 Pass)
- For foreigners whose monthly basic salary is at least S$1,800. S Pass applicants will be assessed on a points system, taking into account multiple criteria including salary, education qualifications, skills, job type and work experience. A levy of S$50 per month will apply and there will be a 5% cap on the number of S Pass holders in each company based on the company's number of local workers and Work Permit holders.
WP Unskilled or semi-skilled foreign workers who wish to work in Singapore must apply for Work Permits in accordance with the Employment of Foreign Workers Act. Work Permits are generally issued according to industrial sectors such as the construction, non-construction and domestic sectors.
希望这些能有所帮助，至于具体的信息，请参考官方网站或者打相关部门询问
人力部(MOM) http://www.mom.gov.sg/
移民局(ICA) http://www.ica.gov.sg/
税务局(IRAS)http://www.iras.gov.sg/
P Pass一般是签发给有一定的学历的专业人士或者管理人员，按照工资的高低具体还分P1、P2两种，工资高于S$7000的P1，工资水平处于S$3500到S$7000的P2
Q1 pass签发对象也是有一定的学历的专业人士，工资高于S$2500的
S Pass的工资必须在1800以上，好像有不少限制
WP一般是签发给普通的工人，比如工地工人等，这个应该是限制最多的
平常大家说的SP一般是指student pass(学生准证),S Pass一般不叫SP
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
WP应该是不能申请PR的，其他的几个似乎都可以(P, Q or S work pass holders;)，至于“不能离境或怀孕之类”这个我没有具体看，不大清楚。
下面你提到的缴税，不管是PR还是持其他什么准证，都是要上税的，具体的上税标准取决于在新加坡上班的天数，少于60天的可以免税，60-183天的税率是15%,超过183天的税率根据年薪算，2万之内的那部分好像是免税的，之后一段一段交(比如说工资超过2万的，前2万是免税的，2万到3万那部分税率3.75%)，是WP和S pass的好像每个月还要交什么劳工税之类，而且每个公司能够雇佣的人数有一定限制，不过具体我也不大清楚。
------------------------------------------------
以下是从人力部(MOM)官方网站拷贝下来的关于不同工作准证的信息
EMPLOYMENT OF LONG-TERM SOCIAL VISIT PASS HOLDER
The Long-Term Social Visit Pass holder is required to obtain an Employment Pass or a Work Permit in order to work in Singapore.
P Pass - For foreigners who hold acceptable degrees, professional qualifications or specialist skills and are seeking professional, administrative, executive or managerial jobs.
*
A P1 Pass will be issued if the applicant's monthly basic salary is more than S$7,000.
*
A P2 Pass will be issued if the applicant's monthly basic salary is more than S$3,500 and up to S$7,000.
Q1 Pass - For foreigners whose monthly basic salary are more than S$2,500 and possess acceptable degrees, professional qualifications or specialist skills.
S Pass (A new category of Work Pass which replaces the Q2 Pass)
- For foreigners whose monthly basic salary is at least S$1,800. S Pass applicants will be assessed on a points system, taking into account multiple criteria including salary, education qualifications, skills, job type and work experience. A levy of S$50 per month will apply and there will be a 5% cap on the number of S Pass holders in each company based on the company's number of local workers and Work Permit holders.
WP Unskilled or semi-skilled foreign workers who wish to work in Singapore must apply for Work Permits in accordance with the Employment of Foreign Workers Act. Work Permits are generally issued according to industrial sectors such as the construction, non-construction and domestic sectors.
希望这些能有所帮助，至于具体的信息，请参考官方网站或者打相关部门询问
人力部(MOM) http://www.mom.gov.sg/
移民局(ICA) http://www.ica.gov.sg/
税务局(IRAS)http://www.iras.gov.sg/
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